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Voltage - Triode (with diode, heptode or hexode) ·Heptode-Triode

12FX8

Triode-heptode front-end tube for 12 V automobile radios. The triode serves as RF amplifier while the heptode combines local-oscillator and mixer functions directly from the vehicle supply.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
2
Base
9KV
Socket code
B9A
Base pins
9
Nominal heater
12.6 V / 270 mA

Description

12FX8 combines a triode and heptode for superheterodyne receivers, serving as a triode RF amplifier and frequency converter from an automotive battery supply.

Socket description

Small-button Noval 9-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
9KV
Socket code
B9A
Base pins
9
Nominal heater voltage
12.6 V
Nominal heater current
270 mA
Parallel heater voltage
-
Parallel heater current
-
Series capable
No

9KV - Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

2 physical sections, each with unique specifications.

Section 1

Heptode

X-ray radiationInterelectrode capacitances
Plate resistance
400000 Ω
Max plate voltage
16 V
Max screen voltage
16 V

Heptode converter section; published ratings/characteristics promoted where applicable.

Section 2

Triode

X-ray radiationInterelectrode capacitances
Transconductance
0.0014 S
Amplification factor
10
Max plate voltage
16 V

Triode RF-amplifier section; published ratings/characteristics promoted where applicable.

Source-dependent data

Operating conditions by source

Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.

Data set 01

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Heptode

Other

  • Heater voltage

    12.6 V

  • Heater current

    270 mA

Characteristic

  • Conversion transconductance

    300 uS

    Converter

  • Oscillator transconductance

    3600 uS

    NotOscillating

Capacitance

  • RF input capacitance

    6 pF

SECTION 2

Triode

Capacitance

  • Grid-to-plate capacitance

    1.3 pF

Data set 02

1966 Tung Sol Electronic Tubes 2 of 4

Published operating points and test conditions from this source.

SECTION 1

Heptode

Capacitance

  • MIXER GRID TO RLATE (G3 TO P) (MAX.)

    0.28 pF

    Interelectrode capacitances

  • MIXER GRID TO

    0 pF

    Interelectrode capacitances; published column 1

  • MIXER GRID TO

    0.12 pF

    Interelectrode capacitances; published column 2

  • MIXER

    0 pF

    Interelectrode capacitances; published column 1

  • MIXER

    24 pF

    Interelectrode capacitances; published column 2

  • MIXER

    5 pF

    Interelectrode capacitances; published column 3

Other

  • HEATER VOLTAGE A

    12.6 V

    Maximum ratings

  • MAXIMUM HEP7

    0 V

    Maximum ratings; published column 1

  • MAXIMUM HEP7

    16 V

    Maximum ratings; published column 2

  • MAXIMUM GRIDS #2 & #4 VOLTAGE

    16 V

    Maximum ratings

  • MAXIMUM GRIDS #2 & #4 SUPPLY VOLTAGE

    16 V

    Maximum ratings

  • MAXIMUM NEGATIVE DC GRID #3 VOLTAGE

    16 V

    Maximum ratings

  • MAXIMUM POSITIVE GRID #} VOLTAGE

    0 V

    Maximum ratings

  • MAXIMUM GRID #3 CIRCUIT RESISTANCE

    10000000 ohm

    Maximum ratings

  • HEATER VOLTAGE

    126 V

    Typical operating conditions

  • GRID #1 VOLTAGE (

    0 V

    Typical operating conditions; published column 1

  • GRID #1 VOLTAGE (

    1.6 V

    Typical operating conditions; published column 2

  • GRID #2 & #4 VOLTAGE (SCREEN GRID)

    12.6 V

    Typical operating conditions

  • GRID #3 VOLTAGE (SIGNAL GRID)

    50 V

    Typical operating conditions

  • PLATE RESISTANCE

    5000000 ohm

    Typical operating conditions

  • TR ANSCONDUCTANCE

    1400 uS

    Typical operating conditions

  • PLATE CURRENT

    29 uA

    Typical operating conditions; published column 1

  • PLATE CURRENT

    0 uA

    Typical operating conditions; published column 2

  • PLATE CURRENT

    1300 uA

    Typical operating conditions; published column 3

  • GRID #2 CURRENT

    1250 uA

    Typical operating conditions

  • CONVERSION TRANSCONDUCTANCE

    3 uS

    Typical operating conditions; published column 1

  • CONVERSION TRANSCONDUCTANCE

    0 uS

    Typical operating conditions; published column 2

  • GRID VOLTAGE FOR

    1 V

    Typical operating conditions; published column 1

  • GRID VOLTAGE FOR

    0 V

    Typical operating conditions; published column 2

  • GRID VOLTAGE FOR

    -3.2 V

    Typical operating conditions; published column 3

  • CONDUCTANCE

    0 uS

    Typical operating conditions; published column 1

  • CONDUCTANCE

    10 uS

    Typical operating conditions; published column 2

  • CONDUCTANCE

    -3 uS

    Typical operating conditions; published column 3

  • GRID #3 VOLTAGE

    0 V

    Typical operating conditions

  • GRIDS #2 & #4~CONNECTED TO PLATE

    12.6 V

    Typical operating conditions

  • CONNECTED TO PLATE

    3600 uS

    Typical operating conditions

  • CATHODE CURRENT

    4.4 mA

    Typical operating conditions

  • GRID #1 VOLTAGE (APPROX.) FOR

    1 V

    Typical operating conditions; published column 1

  • GRID #1 VOLTAGE (APPROX.) FOR

    10 V

    Typical operating conditions; published column 2

  • GRID #1 VOLTAGE (APPROX.) FOR

    -4.5 V

    Typical operating conditions; published column 3

  • CCONVERTER SERVICE-SELF E%CITATION, SCREEN fEEO BALK

    0 ohm

    Maximum ratings; published column 1

  • CCONVERTER SERVICE-SELF E%CITATION, SCREEN fEEO BALK

    11 ohm

    Maximum ratings; published column 2

  • Ef =

    12.6 V

    Maximum ratings

  • Ebb =

    12.6 V

    Maximum ratings

  • Et =

    12.6 V

    Maximum ratings

  • Ebb =

    400 V

    Maximum ratings; published column 2

  • Maximum plate voltage

    16 V

    Published datasheet; promoted section value

  • Maximum screen voltage

    16 V

    Published datasheet; promoted section value

Characteristic

  • Plate resistance

    500000 ohm

    Published datasheet; promoted section value

  • Conversion transconductance

    300 uS

    Heptode converter

SECTION 2

Triode

Capacitance

  • TRIODE GRID TO MIXER GRID (MAX.)

    1 pF

    Interelectrode capacitances

  • TRIODE PLATE TO MIXER GRID (MAX.)

    0.18 pF

    Interelectrode capacitances

  • TRIODE PLATE TO HEPTODE PLATE (MAX.)

    0.2 pF

    Interelectrode capacitances

Other

  • MAXIMUM TRIODE PLATE VOLTAGE ]

    6 V

    Maximum ratings

  • MAXIMUM TRIODE GRID CIRCUIT RESISTANCE

    10000000 ohm

    Maximum ratings

  • Maximum plate voltage

    16 V

    Published datasheet; promoted section value

Characteristic

  • Transconductance

    0.0014 A/V

    Published datasheet; promoted section value

  • Amplification factor

    10

    Published datasheet; promoted section value